The present invention relates to multilayered optical films having a composition that allows for recycling of scrap material from the films into one or more layers of subsequent films and to multilayered optical films having one or more layers made using material recycled from previously manufactured films.
Polymeric films are used in a wide variety of applications. One particular use of polymeric films is in mirrors and polarizers which reflect light of a given polarization and wavelength range. Such reflective films are used, for example, in conjunction with backlights in liquid crystal displays to enhance brightness and reduce glare of the display. A polarizing film may be placed between the user and the backlight to direct the light towards the user and to polarize the light; thereby reducing the glare. In addition, a mirror film may be placed behind the backlight to reflect light towards the user; thereby enhancing brightness. Another use of polarizing films is in articles, such as sunglasses, to reduce light intensity and glare.
One type of polymer that is useful in creating polarizer or mirror films is a polyester. One example of a polyester-based polarizer includes a stack of polyester layers of differing composition. One configuration of this stack of layers includes a first set of birefringent layers and a second set of layers with an isotropic index of refraction. The second set of layers alternates with the birefringent layers to form a series of interfaces for reflecting light. The polarizer may also include one or more non-optical layers which, for example, cover at least one surface of the stack of layers to prevent damage to the stack during or after processing. There are other configurations that may also be used in polarizer/mirror films including stacks of layers with two or more different sets of birefringent and/or isotropic layers.
The properties of a given polyester are typically determined by the monomer materials utilized in the preparation of the polyester. A polyester is often prepared by reactions of one or more different carboxylate monomers (e.g., compounds with two or more carboxylic acid or ester functional groups) with one or more different glycol monomers (e.g., compounds with two or more hydroxy functional groups). Each set of polyester layers in the stack typically has a different combination of monomers to generate the desired properties for each type of layer.
With the manufacture of polarizers and mirrors, an amount of scrap material is generated due to activities such as sizing and trimming the film. This scrap material typically contains a mixture of the various layers that are used in the polymer film. It is desirable to find a use for this scrap material to reduce waste.
Generally, the present invention relates to a multilayered polymer film. One embodiment is a multilayered optical film having a stack of layers which includes one or more first optical layers made from a first polymeric material; one or more second optical layers made from a second polymeric material; and one or more non-optical layers made from recycled polymeric material. The one or more non-optical layers are provided within the stack of layers in such a way that at least a portion of the light passing through the one or more first and second optical layers also passes through at least one of the non-optical layers.
Another embodiment is a multilayered polymer film with a stack of layers that includes one or more first optical layers, one or more second optical layers, and one or more non-optical layers. The one or more first optical layer are made from a first polyester which includes first carboxylate subunits. The one or more second optical layers are made from a second polyester which includes second carboxylate subunits that are different than the first carboxylate subunits. The one or more non-optical layers are made from a third polyester which includes the first and second carboxylate subunits in the same relative molar proportions as the molar proportions of the first and second carboxylate subunits in a combination of all the first and second optical layers of the multilayered polymer film.
Another embodiment is a multilayered polymer film with a stack of layers that includes one or more first optical layers, one or more second optical layers, and one or more non-optical layers. The one or more first optical layers are made from a first polyester which includes first glycol subunits. The one or more second optical layers are made from a second polyester which includes second glycol subunits that are different than the first glycol subunits. The one or more non-optical layers are made from a third polyester which includes the first and second glycol subunits in the same relative molar proportions as the molar proportions of the first and second glycol subunits in a combination of all the first and second optical layers of the multilayered polymer film. In some instances, the second polyester includes third carboxylate subunits, which can be the same as the first carboxylate subunits of the first polyester. Also, in some instances, the first polyester includes fourth carboxylate subunits.
Another embodiment is a multilayered optical film having a stack of layers with one or more first optical layers, one or more second optical layers, and one or more non-optical layers. The one or more first optical layers are made with a first polyester. The one or more second layers are made with a second polyester. The one or more non-optical layers are made with a polyester material that is recycled from one or more prior-manufactured multilayered polymer films
A further embodiment is a non-optical layer for use in a stack of layers forming a multilayered optical film. The non-optical layer is made from polyester material which is recycled from one or more prior-manufactured multilayered polymer films.
Yet another embodiment is a method for making a multilayered optical film which includes obtaining scrap material generated by the prior manufacture of one or more multilayered polymer films and forming a multilayered polymer film which contains a stack of layers. The stack of layers includes one or more first optical layers, one or more second optical layers, and one or more non-optical layers. The one or more non-optical layers being formed with the scrap material.
The above summary of the present invention is not intended to describe each illustrated embodiment or every implementation of the present invention. The figures and the detailed description which follow more particularly exemplify these embodiments.